A cathode ray tube (CRT) is generally used as a monitor for a television (TV), a measuring instrument, an information terminal, and the like. However, due to the weight and size of the CRT, it is difficult to reduce the weight and size of an electronic device incorporating a CRT.
In order to replace the CRT, a liquid crystal display (LCD) device having a variety of advantages in terms of the size, weight and electric power consumption has been developed. The LCD has been applied to a variety of electronic devices such as a monitor for a laptop computer as well as a desktop computer and a large-sized display unit. Therefore, it is expected that demand for the LCDs will sharply increased in the future.
The LCD is designed to convert a specific orientation of liquid crystal molecules into other orientations by applying a voltage to the liquid crystal molecules. That is, the LCD is designed to convert the variation of the optical properties such as birefringence, circumpolarization, dichroism, and light scattering into a visual variation. The LCD is a display device using a light modulation by a liquid crystal cell.
Unlike the CRT, the LCD does emit light by itself. Therefore, in order to visually represent an image on a surface of the liquid crystal panel, a light source such as a backlight unit having, for example, a cold cathode fluorescent lamp (CCFL) is needed.
FIG. 1 is a perspective view of a conventional LCD and FIG. 2 is a sectional view taken along line I-I′ of FIG. 1. A conventional LCD is generally divided into a liquid crystal panel 8 for display of an image and a backlight unit for emitting light to the liquid crystal panel.
The backlight unit includes a lamp 1 emitting light, a light guide plate 2 for converting the light emitted from the lamp 1 into a surface-emitted light and guiding the surface-emitted light to the liquid crystal panel 8 at a place under the liquid crystal panel 8, a lamp housing enclosing the lamp 1, a reflective plate 4 disposed below the light guide plate 2 to reflect the light toward the liquid crystal panel 8, and an optical sheet unit 5 disposed above the light guide plate 2 to diffuse and focus the surface emitted light from the light guide plate 2. The optical sheet unit 5 includes a diffuser sheet, a prism sheet and a protector sheet.
The liquid crystal panel 8 and the backlight unit are assembled on a mold frame 6 and upper and lower cases 10 and 9 are respectively assembled on upper and lower portions of a mold frame 6 to protect the components from external impact or vibration.
In order to prevent the lamp 1 from being damaged by the movement of the light guide plate in the mold frame, clips 7 are provided at corner regions of the mold frame 6.
The clips 7 are disposed between the lamp 1 and the light guide plate 2. The clips 7 must have sufficient strength such that they can endure an impact force applied by the movement of the light guide plate 2.
As shown in FIG. 3, the mold frame 6 and the light guide plate 2 are assembled with each other and the clips 7 are provided at regions corresponding to end regions of the lamp (not shown).
The clip 7 is formed of a dark metal material and is shaped in a right angle. The clips 7 function to prevent the light guide plate 2 from moving into the lamp region, thereby preventing the lamp from being damaged or broken.
However, this method using the clips 7 cannot sufficiently prevent the lamp from being damaged or broken by the movement of the light guide plate. In an actual impact test, it is noted that the lamps are frequently damaged or broken even when the clips 7 are attached on the mold frame 6.
In addition, the attachment of the clips 7 to the mold frame makes the manufacturing process complicated as an additional tool is required to attach the clips 7. This increases the manufacturing costs. In addition, during the attachment of the clips 7, foreign objects are frequently formed on the backlight unit.
Since the clips 7 are formed of the dark metal material, they reflect the light, thereby forming dark regions at the corner regions of the light guide plate 2, thus deteriorating the luminance of the corner regions of the liquid crystal panel. This results in the deterioration of the overall display quality of the LCD.
Since the clips 7 are formed of the metal, the heat generated from the lamp is transmitted to the light guide plate 2 via the clips 7. This may cause the light guide plate 2 to soften or melt.